1. Field of the Invention
The present invention relates generally to lumen designs for catheters. More particularly, the invention relates to lumen designs for catheters that modify and control the temperature of a selected body organ.
2. Background Information
Organs in the human body, such as the brain, kidney and heart, are maintained at a constant temperature of approximately 37xc2x0 C. Hypothermia can be clinically defined as a core body temperature of 35xc2x0 C. or less. Hypothermia is sometimes characterized further according to its severity. A body core temperature in the range of 33xc2x0 C. to 35xc2x0 C. is described as mild hypothermia. A body temperature of 28xc2x0 C. to 32xc2x0 C. is described as moderate hypothermia. A body core temperature in the range of 24xc2x0 C. to 28xc2x0 C. is described as severe hypothermia.
Hypothermia is uniquely effective in reducing brain injury caused by a variety of neurological insults and may eventually play an important role in emergency brain resuscitation. Experimental evidence has demonstrated that cerebral cooling improves outcome after global ischemia, focal ischemia, or traumatic brain injury. For this reason, hypothermia may be induced in order to reduce the effect of certain bodily injuries to the brain as well as other organs.
Cerebral hypothermia has traditionally been accomplished through whole body cooling to create a condition of total body hypothermia in the range of 20xc2x0 C. to 30xc2x0 C.
Catheters have been developed which are inserted into the bloodstream of the patient in order to induce total body hypothermia. For example, U.S. Pat. No. 3,425,419 to Dato describes a method and apparatus of lowering and raising the temperature of the human body. Dato induces moderate hypothermia in a patient using a metallic catheter. The metallic catheter has an inner passageway through which a fluid, such as water, can be circulated. The catheter is inserted through the femoral vein and then through the inferior vena cava as far as the right atrium and the superior vena cava. The Dato catheter has an elongated cylindrical shape and is constructed from stainless steel. By way of example, Dato suggests the use of a catheter approximately 70 cm in length and approximately 6 mm in diameter.
Due to certain problems sometimes associated with total body hypothermia, attempts have been made to provide more selective cooling. For example, cooling helmets or headgear have been used in an attempt to cool only the head rather than the patient""s entire body. However, such methods rely on conductive heat transfer through the skull and into the brain. One drawback of using conductive heat transfer is that the process of reducing the temperature of the brain is prolonged. Also, it is difficult to precisely control the temperature of the brain when using conduction due to the temperature gradient that must be established externally in order to sufficiently lower the internal temperature. In addition, when using conduction to cool the brain, the face of the patient is also subjected to severe hypothermia, increasing discomfort and the likelihood of negative side effects. It is known that profound cooling of the face can cause similar cardiovascular side effects as total body cooling. From a practical standpoint, such devices are cumbersome and may make continued treatment of the patient difficult or impossible.
Selected organ hypothermia has been accomplished using extracorporeal perfusion, as detailed by Arthur E. Schwartz, M.D. et al., in Isolated Cerebral Hypothermia by Single Carotid Artery Perfusion of Extracorporeally Cooled Blood in Baboons, which appeared in Vol. 39, No. 3, Neurosurgery 577 (September, 1996). In this study, blood was continually withdrawn from baboons through the femoral artery. The blood was cooled by a water bath and then infused through a common carotid artery with its external branches occluded. Using this method, normal heart rhythm, systemic arterial blood pressure and arterial blood gas values were maintained during the hypothermia. This study showed that the brain could be selectively cooled to temperatures of 20xc2x0 C. without reducing the temperature of the entire body. However, external circulation of blood is not a practical approach for treating humans because the risk of infection, need for anticoagulation, and risk of bleeding is too great. Further, this method requires cannulation of two vessels making it more cumbersome to perform particularly in emergency settings. Even more, percutaneous cannulation of the carotid artery is difficult and potentially fatal due to the associated arterial wall trauma. Finally, this method would be ineffective to cool other organs, such as the kidneys, because the feeding arteries cannot be directly cannulated percutaneously.
Selective organ hypothermia has also been attempted by perfusion of a cold solution such as saline or perflourocarbons. This process is commonly used to protect the heart during heart surgery and is referred to as cardioplegia. Perfusion of a cold solution has a number of drawbacks, including a limited time of administration due to excessive volume accumulation, cost, and inconvenience of maintaining the perfusate and lack of effectiveness due to the temperature dilution from the blood. Temperature dilution by the blood is a particular problem in high blood flow organs such as the brain.
Catheters adapted for delivering heat transfer fluids at temperatures above or below normal body temperatures to selected internal body sites have been devised in the past (See, for example, U.S. Pat. No. 5,624,392 to Saab). These catheters often have a concentric, coaxial configuration of multiple lumens. The configurations often have a first central lumen adapted to receive a guide surrounded by a concentric second supply lumen adapted to supply a working fluid to a distal portion of the catheter and an outer concentric third return lumen, which surrounds the second lumen, adapted to return a working fluid to a fluid source. A problem with this configuration is that the working fluid in the supply lumen makes surface area contact with both an outer wall, which partially defines the outer limits of the second lumen, and an inner wall, which defines the first lumen, leading to increased heat transfer between the walls and the working fluid. Thus, if the second supply lumen in the catheter is designed to deliver a cooling fluid to the distal portion of the catheter, the increased surface area contact caused by this configuration unnecessarily warms the cooling fluid prior to delivery to the distal portion of the catheter. Another problem with these catheters is that the supply lumen(s) and return lumen(s) are not sized relative to each other to maximize the flow rate through the catheter. Hence, they do not optimize heating and/or cooling catheter performance.
The present invention involves a device for heating or cooling a surrounding fluid in a blood vessel that addresses and solves the problems discussed above with multiple lumen arrangements of catheters in the past. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior, an elongated supply lumen adapted to deliver a working fluid to the interior of the heat transfer element and having a hydraulic diameter, an elongated return lumen adapted to return a working fluid from the interior of the heat transfer element and having a hydraulic diameter, and wherein the ratio of the hydraulic diameter of the return lumen to the hydraulic diameter of the supply lumen is substantially equal to 0.75.
Implementations of the above aspect of the invention may include one or more of the following. The supply lumen may be disposed substantially within the return lumen. One of the supply lumen and return lumen may have a cross-sectional shape that is substantially luniform. One of the supply lumen and the return lumen has a cross-sectional shape that is substantially annular. The supply lumen has a general cross-sectional shape and the return lumen has a general cross-sectional shape different from the general cross-sectional shape of the supply lumen. The catheter assembly includes an integrated elongated bi-lumen member having a first lumen adapted to receive a guide wire and a second lumen comprising either the supply lumen or the return lumen. The bi-lumen member has a cross-sectional shape that is substantially in the shape of a figure eight. The first lumen has a cross-sectional shape that is substantially circular and the second lumen has a cross-sectional shape that is substantially annular. The heat transfer element includes means for inducing mixing in a surrounding fluid. The device further includes means for inducing wall jets or means for further enhancing mixing of the working fluid to effect further heat transfer between the heat transfer element and working fluid. The heat transfer element includes an interior distal portion and the supply lumen includes first means for delivering working fluid to the interior distal portion of the heat transfer element and second means for delivering working fluid to the interior of the heat transfer element at one or more points point proximal to the distal portion of the heat transfer element.
A second aspect of the invention involves a catheter assembly capable of insertion into a selected blood vessel in the vascular system of a patient. The catheter assembly includes an elongated catheter body including an operative element having an interior at a distal portion of the catheter body, an elongated supply lumen adapted to deliver a working fluid to the interior of the distal portion and having a hydraulic diameter, an elongated return lumen adapted to return a working fluid from the interior of the operative element and having a hydraulic diameter, and wherein the ratio of the hydraulic diameter of the return lumen to the hydraulic diameter of the supply lumen being substantially equal to 0.75.
Any of the implementations described above with respect to the first aspect of the invention also apply to the second aspect of the invention. Further, implementations of the second aspect of the invention may include one or more of the following. The operative element may include a heat transfer element adapted to transfer heat to or from the working fluid. The heat transfer element may include means for inducing mixing in a surrounding fluid. The operative element may include a catheter balloon adapted to be inflated with the working fluid.
A third aspect of the invention involves a device for heating or cooling a surrounding fluid in a vascular blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior, an integrated elongated bi-lumen member located within the catheter body and including a first lumen adapted to receive a guide wire and a second lumen, the second lumen comprising either a supply lumen to deliver a working fluid to an interior of the heat transfer element or a return lumen to return a working fluid from the interior of the heat transfer element, and a third lumen comprising either a supply lumen to deliver a working fluid to an interior of the heat transfer element or a return lumen to return a working fluid from the interior of the heat transfer element.
Implementations of the third aspect of the invention may include one or more of the following. The catheter body includes an internal wall and the integrated bi-lumen member includes an exterior wall, and the third lumen is substantially defined by the internal wall of the catheter body and the exterior wall of the bi-lumen member. Both the catheter body and the bi-lumen member are extruded. The bi-lumen member is disposed substantially within the third lumen. The second lumen has a cross-sectional shape that is substantially luniform. The third lumen has a cross-sectional shape that is substantially annular. The second lumen has a general cross-sectional shape and the third lumen has a general cross-sectional shape different from the general cross-sectional shape of the second lumen. The bi-lumen member has a cross-sectional shape that is substantially in the shape of a figure eight. The first lumen has a cross-sectional shape that is substantially circular and the second lumen has a cross-sectional shape that is substantially luniform. The heat transfer element includes means for inducing mixing in a surrounding fluid. The device further includes means for inducing wall jets or means for further enhancing mixing of the working fluid to effect further heat transfer between the heat transfer element and working fluid. The heat transfer element includes an interior distal portion and the supply lumen includes first means for delivering working fluid to the interior distal portion of the heat transfer element and second means for delivering working fluid to the interior of the heat transfer element at one or more points point proximal to the distal portion of the heat transfer element.
A fourth aspect of the present invention involves a catheter assembly capable of insertion into a selected blood vessel in the vascular system of a patient. The catheter assembly includes an elongated catheter body including an operative element having an interior at a distal portion of the catheter body, an integrated elongated bi-lumen member located within the catheter body and including a first lumen adapted to receive a guide wire and a second lumen, the second lumen comprising either a supply lumen to deliver a working fluid to the interior of the operative element or a return lumen to return a working fluid from the interior of the operative element, and a third lumen within the catheter body and comprising either a supply lumen to deliver a working fluid to an interior of the operative element or a return lumen to return a working fluid from the interior of the operative element.
Any of the implementations described above with respect to the third aspect of the invention also apply to the fourth aspect of the invention.
A fifth aspect of the invention involves a method of manufacturing a catheter assembly for heating or cooling a surrounding fluid in a blood vessel. The method involves extruding an elongated catheter body; locating a heat transfer element including an interior at a distal portion of the catheter body; extruding an integrated elongated bi-lumen member including a first lumen adapted to receive a guide wire and a second lumen, the second lumen comprising either a supply lumen to deliver a working fluid to an interior of the heat transfer element or a return lumen to return a working fluid from the interior of the heat transfer element; and providing the integrated bi-lumen member substantially within the elongated catheter body so that a third lumen is formed, the third lumen comprising either a supply lumen to deliver a working fluid to an interior of the heat transfer element or a return lumen to return a working fluid from the interior of the heat transfer element.
Implementations of the fifth aspect of the invention may include one or more of the following. The second lumen has a hydraulic diameter and the third lumen has a hydraulic diameter, and the ratio of the hydraulic diameter of the second lumen to the hydraulic diameter of the third lumen is substantially equal to 0.75. The step of providing the integrated bi-lumen member substantially within the elongated catheter body includes simultaneously extruding the integrated bi-lumen member substantially within the elongated catheter body.
A sixth aspect of the present invention involves a method of manufacturing a catheter assembly. The method includes extruding an elongated catheter body; locating an operative element including an interior at a distal portion of the catheter body; extruding an integrated elongated bi-lumen member including a first lumen adapted to receive a guide wire and a second lumen, the second lumen comprising either a supply lumen to deliver a working fluid to an interior of the operative element or a return lumen to return a working fluid from the interior of the operative element; and providing the integrated bi-lumen member substantially within the elongated catheter body so that a third lumen is formed, the third lumen comprising either a supply lumen to deliver a working fluid to an interior of the operative element or a return lumen to return a working fluid from the interior of the operative element.
Any of the implementations described above with respect to the fifth aspect of the invention also apply to the sixth aspect of the invention.
A seventh aspect of the present invention involves a device for heating or cooling a surrounding fluid in a blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior distal portion and an interior portion defining at least a first heat transfer segment and a second heat transfer segment, and at least one elongated supply lumen located within the catheter body, the at least one elongated supply lumen including first means for delivering working fluid to the interior distal portion of the first heat transfer segment and second means for delivering working fluid to the interior portion of the second heat transfer segment.
In an implementation of the seventh aspect of the invention, the second working fluid delivering means is adapted to deliver working fluid to the interior portion of the heat transfer element near a midpoint of the heat transfer element.
An eighth aspect of the present invention involves a device for heating or cooling a surrounding fluid in a blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior distal portion and an interior portion, and at least one elongated supply lumen located within the catheter body, the at least one elongated supply lumen including first means for delivering working fluid to the interior distal portion of the heat transfer element and second means for delivering working fluid to the interior portion of the heat transfer element at one or more points proximal to the distal portion of the heat transfer element.
In an implementation of the eighth aspect of the invention, the second working fluid delivering means is adapted to deliver working fluid to the interior portion of the heat transfer element near a midpoint of the heat transfer element.
A ninth aspect of the present invention involves a device for heating or cooling a surrounding fluid in a blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior distal portion and an interior portion defining at least a first heat transfer segment and a second heat transfer segment, a first elongated supply lumen located within the catheter body and terminating at the interior distal portion of the heat transfer element into first means for delivering working fluid to the interior distal portion of the heat transfer element, and a second elongated supply lumen located within the catheter body and terminating at a point proximal to the distal portion of the heat transfer element into second means for delivering working fluid to the interior portion of the heat transfer element at a point proximal to the distal portion of the heat transfer element.
In an implementation of the ninth aspect of the invention, the second working fluid delivering means is adapted to deliver working fluid to the interior portion of the heat transfer element near a midpoint of the heat transfer element.
A tenth aspect of the present invention involves a device for heating or cooling a surrounding fluid in a blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior distal portion and an interior portion defining at least a first heat transfer segment interior portion and a second heat transfer segment interior portion, a first elongated supply lumen located within the catheter body and terminating at the interior distal portion of the first heat transfer segment into first means for delivering working fluid to the interior of the first heat transfer segment, and a second elongated supply lumen located within the catheter body and terminating at a point proximal to the distal portion of the heat transfer element into second means for delivering working fluid to the interior portion of the second heat transfer segment.
In an implementation of the tenth aspect of the invention, the second working fluid delivering means is adapted to deliver working fluid to the interior portion of the heat transfer element near a midpoint of the heat transfer element.
An eleventh aspect of the present invention involves a device for heating or cooling a surrounding fluid in a blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior portion adapted to induce mixing of a working fluid to effect heat transfer between the heat transfer element and working fluid, the heat transfer element including at least a first heat transfer segment, a second heat transfer segment, and an intermediate segment between the first heat transfer segment and the second heat transfer segment, an elongated supply lumen member located within the catheter body and adapted to deliver the working fluid to the interior of the heat transfer element, the supply lumen member including a circular outer surface, an elongated return lumen defined in part by the outer surface of the supply lumen member and the interior portion of the heat transfer element and adapted to return the working fluid from the interior of the heat transfer element, and wherein the distance between the interior portion of the heat transfer element and the outer surface of the supply lumen member adjacent the intermediate segment is less than the distance between the interior portion of the heat transfer element and the outer surface of the supply lumen member adjacent the first heat transfer segment.
Implementations of the eleventh aspect of the invention may include one or more of the following. The distance between the interior portion of the heat transfer element and the outer surface of the supply lumen member adjacent the intermediate segment is such that the characteristic flow resulting from a flow of working fluid is at least of a transitional nature. The intermediate segment includes an interior diameter that is less than the interior diameter of the first heat transfer segment or the second heat transfer segment. The supply lumen member includes an outer diameter adjacent the intermediate segment that is greater than its outer diameter adjacent the first heat transfer segment or the second heat transfer segment. The supply lumen member comprises a multiple-lumen member. The supply lumen member includes a supply lumen having a hydraulic diameter and the return lumen has a hydraulic diameter substantially equal to 0.75 the hydraulic diameter of the supply lumen. The intermediate segment includes a flexible bellows joint.
A twelfth aspect of the present invention involves a device for heating or cooling a surrounding fluid in a blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior portion adapted to induce mixing of a working fluid to effect heat transfer between the heat transfer element and working fluid, an elongated supply lumen member located within the catheter body and adapted to deliver the working fluid to the interior of the heat transfer element, an elongated return lumen member located within the catheter body and adapted to return the working fluid from the interior of the heat transfer element, and means located within the heat transfer element for further enhancing mixing of the working fluid to effect further heat transfer between the heat transfer element and working fluid.
Implementations of the twelfth aspect of the invention may include one or more of the following. The supply lumen member comprises a multiple-lumen member having a circular outer surface. The supply lumen member includes a supply lumen having a hydraulic diameter and the return lumen has a hydraulic diameter substantially equal to 0.75 of the hyrdraulic diameter of the supply lumen.
A thirteenth aspect of the present invention involves a device for heating or cooling a surrounding fluid in a blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior portion adapted to induce mixing of a working fluid to effect heat transfer between the heat transfer element and working fluid, an elongated supply lumen member located within the catheter body and adapted to deliver the working fluid to the interior of the heat transfer element, an elongated return lumen member located within the catheter body and adapted to return the working fluid from the interior of the heat transfer element, and a mixing-enhancing mechanism located within the heat transfer element and adapted to further mix the working fluid to effect further heat transfer between the heat transfer element and working fluid.
Implementations of the thirteenth aspect of the invention may include one or more of the following. The supply lumen member comprises a multiple-lumen member having a circular outer surface. The supply lumen member includes a supply lumen having a hydraulic diameter and the return lumen has a hydraulic diameter substantially equal to the hydraulic diameter of the supply lumen.
A fourteenth aspect of the present invention involves a method of heating or cooling a surrounding fluid in a blood vessel. The method includes providing a device for heating or cooling a surrounding fluid in a blood vessel within the blood stream of a blood vessel, the device including an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior portion adapted to induce mixing of a working fluid to effect heat transfer between the heat transfer element and working fluid, an elongated supply lumen member located within the catheter body and adapted to deliver the working fluid to the interior of the heat transfer element, an elongated return lumen member located within the catheter body and adapted to return the working fluid from the interior of the heat transfer element, and a mixing-enhancing mechanism located within the heat transfer element and adapted to further mix the working fluid to effect further heat transfer between the heat transfer element and working fluid; causing a working fluid to flow to and along the interior portion of the heat transfer element of the device using the supply lumen and return lumen; facilitating the transfer of heat between the working fluid and the heat transfer element by effecting mixing of the working fluid with the interior portion adapted to induce mixing of a working fluid; facilitating additional transfer of heat between the working fluid and the heat transfer element by effecting further mixing of the working fluid with the interior portion with the mixing-enhancing mechanism; causing heat to be transferred between the blood stream and the heat transfer element by the heat transferred between the heat transfer element and working fluid.
The novel features of this invention, as well as the invention itself, will be best understood from the attached drawings, taken along with the following description, in which similar reference characters refer to similar parts, and in which: